Photopolymerizable compositions comprising added dyes are known. Conventionally, the dye may be added for one or several reasons. As described, for example, in Baum and Henry, U.S. Pat. No. 3,652,275, and in Dueber, U.S Pat. No. 4,162,162, the added dye, generally known as a sensitizer, can absorb actinic radiation and activate the photoinitiation process. As described, for example, in Held, U.S. Pat. No. 3,854,950, the added dye, generally known as an antihalation agent, can absorb scattered and reflected actinic radiation an improve the resolution of the resulting photopolymer image. The added dye may also provide color to facilitate visual inspection of the resulting exposed and washed-out photopolymer image.
To be effective, antihalation agents must absorb the scattered and reflected actinic radiation. Therefore, they must absorb the same region of the spectrum as the photoinitiator system, and, thus, will absorb part of the incident actinic radiation as well Consequently, improved resolution is accomplished at a loss in photospeed.
Photopolymerizable compositions containing two added dyes are known. In Sato, U.S. Pat. No. 4,268,603, a photocrosslinkable photoresist system comprising a bis-azide; a photoextinction agent, which has its absorption maximum at a longer wavelength than the bis-azide; and a fluorescent agent, which absorbs at the same wavelength as the bis-azide, but fluoresces at a wavelength which is absorbed by the photoextinction agent, is disclosed. In this composition, the loss of ultra-violet absorption at about 360 nm, the wavelength of the incident actinic radiation, caused by photodecomposition of the bis-azide as the photoreaction proceeds is compensated for by formation of a photodegradation product which absorbs at 360 nm from the photodegradation of the photoextinction agent. Photodegradation of the photoextinction agent is initiated by the radiation emitted by the fluorescent agent. Thus, the optical density of the composition at 360 nm remains essentially constant throughout the exposure, and the amount of light reflected by the support does not increase as reaction proceeds. However, in this system part of the actinic radiation is absorbed by the fluorescent agent.